Process for the synthesis of ethers of aromatic acids

ABSTRACT

Ethers of aromatic acids are produced from halogenated aromatic acids in a reaction mixture containing a copper (I) or copper (II) source and a diamine ligand that coordinates to copper.

This application claims the benefit of U.S. Provisional Application No.60/876,575, filed 21 Dec. 2006, which is incorporated in its entirety asa part hereof for all purposes.

TECHNICAL FIELD

This invention relates to the manufacture of ethers of hydroxy aromaticacids, which are valuable for a variety of purposes such as use asintermediates or as monomers to make polymers.

BACKGROUND

Ethers of aromatic acids are useful as intermediates and additives inthe manufacture of many valuable materials including pharmaceuticals andcompounds active in crop protection, and are also useful as monomers inthe production of high-performance rigid rod polymers, for example,linear rigid oligoanthranilamides for electronic applications [Wu et al,Organic Letters (2004), 6(2), 229-232] and polypyridobisimidazoles andthe like (see e.g. Beers et al, High-Performance Fibres (2000), 93-155].

Existing processes to produce 2,5-dialkoxy- and2,5-diarenoxyterephthalic acid involve stepwise alkylation of2,5-dihydroxyterephthalic acid to form the corresponding 2,5-alkoxy- and2,5-diarenoxyterephthalic esters followed by dealkylation of the esterto the acid. An n-hydroxy aromatic acid may be converted to an n-alkoxyaromatic acid by contacting the hydroxy aromatic acid under basicconditions with an n-alkyl sulfate. One suitable method of running sucha conversion reaction is as described in Austrian Patent No. 265,244.Yields are moderate to low, productivity is low and a two-step processis necessary.

A need therefore remains for a process by which ethers of aromatic acidscan be produced economically and with high yields and high productivityin small- and large-scale operation, and in batch and continuousoperation.

SUMMARY

The inventions disclosed herein include processes for the preparation ofan ether of an aromatic acid, processes for the preparation of productsinto which such an ether can be converted, the use of such processes,and the products obtained and obtainable by such processes.

One embodiment of the processes hereof provides a process for preparingan ether of an aromatic acid, the ether being described by the structureof Formula I

wherein Ar is a C₆˜C₂₀ monocyclic or polycyclic aromatic nucleus, R is aunivalent organic radical, n and m are each independently a nonzerovalue, and n+m is less than or equal to 8; by

(a) contacting a halogenated aromatic acid that is described by thestructure of Formula II

wherein each X is independently Cl, Br or I, and Ar, n and m are as setforth above, with

-   -   (i) a polar protic solvent, a polar aprotic solvent or an        alcoholic solvent containing the alcoholate RO⁻M⁺ (wherein M is        Na or K), wherein the polar protic solvent, polar aprotic        solvent or alcoholic solvent is either ROH or is a solvent that        is less acidic than ROH;    -   (ii) a copper (I) or copper (II) source; and    -   (iii) a diamine ligand that coordinates to copper,        to form a reaction mixture;

(b) heating the reaction mixture to form the m-basic salt of the productof step (a), as described by the structure of Formula III;

(c) optionally, separating the Formula III m-basic salt from thereaction mixture in which it is formed; and

(d) contacting the Formula III m-basic salt with acid to form therefroman ether of an aromatic acid.

Another embodiment of this invention provides a process for preparing acompound, monomer, oligomer or polymer by preparing an ether of anaromatic acid that is described by the structure of Formula I, and thensubjecting the ether so produced to a reaction (including a multi-stepreaction) to prepare therefrom a compound, monomer, oligomer or polymer.

DETAILED DESCRIPTION

This invention provides a process having improved yield and productivityfor preparing an ether of an aromatic acid, the ether being described bythe structure of Formula I

wherein Ar is a C₆˜C₂₀ monocyclic or polycyclic aromatic nucleus, R is aunivalent organic radical, n and m are each independently a nonzerovalue, and n+m is less than or equal to 8.

One embodiment of such a process proceeds by (a) contacting ahalogenated aromatic acid that is described by the structure of FormulaII

wherein each X is independently Cl, Br or I, and Ar, n and m are as setforth above, with

-   -   (i) a polar protic solvent, a polar aprotic solvent or an        alcoholic solvent containing the alcoholate RO⁻M⁺ (wherein M is        Na or K), wherein the polar protic solvent, polar aprotic        solvent or alcoholic solvent is either ROH or is a solvent that        is less acidic than ROH;    -   (ii) a copper (I) or copper (II) source; and    -   (iii) a diamine ligand that coordinates to copper,        to form a reaction mixture;

(b) heating the reaction mixture to form the m-basic salt of the productof step (a), as described by the structure of Formula III;

(c) optionally, separating the Formula III m-basic salt from thereaction mixture in which it is formed; and

(d) contacting the Formula III m-basic salt with acid to form therefroman ether of an aromatic acid.

In Formulae I, II and III, Ar is a C₆˜C₂₀ monocyclic or polycyclicaromatic nucleus; n and m are each independently a nonzero value and n+mis less than or equal to 8; R is a univalent organic radical; and inFormula II, each X is independently Cl, Br or I.

The radical denoted by

is an n+m valent C₆˜C₂₀ monocyclic or polycyclic aromatic nucleus formedby the removal of n+m hydrogens from different carbon atoms on thearomatic ring, or on the aromatic rings when the structure ispolycyclic. The radical “Ar” may be substituted or unsubstituted; whenunsubstituted, it contains only carbon and hydrogen.

One example of a suitable Ar group is phenylene, as shown below, whereinn=m=1.

A preferred Ar group is shown below, wherein n=m=2.

The univalent radical R is a univalent organic radical. Preferably, R isa C₁˜C₁₂ alkyl group or an aryl group. More preferably, R is a C₁˜C₄alkyl group or phenyl. Examples of particularly suitable R groupsinclude without limitation methyl, ethyl, i-propyl, i-butyl, and phenyl.Several other nonlimiting examples of R are shown below:

An “m-basic salt”, as the term is used herein, is the salt formed froman acid that contains in each molecule m acid groups having areplaceable hydrogen atom.

Various halogenated aromatic acids, to be used as a starting material inthe process of this invention, are commercially available. For example,2-bromobenzoic acid is available from Aldrich Chemical Company(Milwaukee, Wis.). It can be synthesized, however, by oxidation ofbromomethylbenzene as described in Sasson et al, Journal of OrganicChemistry (1986), 51(15), 2880-2883. Other halogenated aromatic acidsthat can be used include without limitation 2,5-dibromobenzoic acid,2-bromo-5-nitrobenzoic acid, 2-bromo-5-methylbenzoic acid,2-chlorobenzoic acid, 2,5-dichlorobenzoic acid,2-chloro-3,5-dinitrobenzoic acid, 2-chloro-5-methylbenzoic acid,2-bromo-5-methoxybenzoic acid, 5-bromo-2-chlorobenzoic acid,2,3-dichlorobenzoic acid, 2-chloro-4-nitrobenzoic acid,2,5-dichloroterephthalic acid, 2-chloro-5-nitrobenzoic acid,2,5-dibromoterephthalic acid, and 2,5-dichloroterephthalic acid, all ofwhich are commercially available. Preferably, the halogenated aromaticacid is 2,5-dibromoterephthalic acid or 2,5-dichloroterephthalic acid.

Other halogenated aromatic acids useful as a starting material in theprocess of this invention include those shown in the left column of thetable below, wherein X═Cl, Br or I, and wherein the corresponding etherof an aromatic acid produced therefrom by the process of this inventionis shown in the right column:

(COOH)_(m)—Ar—(X)_(n) I (COOH)_(m)—Ar—(OR)_(n) II

In step (a), a halogenated aromatic acid is contacted with a polarprotic or polar aprotic solvent or alcoholic solvent containing thealcoholate RO⁻M⁺, wherein R is as defined above and M is Na or K; acopper (I) or copper (II) source; and a diamine ligand that coordinatesto copper.

The alcohol may be ROH, which is preferred, or it may be an alcohol thatis not more acidic than ROH. For example, if R is phenyl, such that ROHis phenol, then one nonlimiting example of a less acidic alcohol thatcan be used in step (a) is isopropanol. Examples of suitable alcoholsinclude without limitation methanol, ethanol, i-propanol, i-butanol, andphenol, with the proviso that the alcohol is either ROH or an alcoholthat is not more acidic than ROH.

The solvent may also be a polar protic or polar aprotic solvent or amixture of protic or polar aprotic solvent. A polar solvent, as usedherein, is a solvent whose constituent molecules exhibit a nonzerodipole moment. A polar protic solvent, as used herein, is a polarsolvent whose constituent molecules contain an O—H or N—H bond. A polaraprotic solvent, as used herein, is a polar solvent whose constituentmolecules do not contain an O—H or N—H bond. Examples of polar solventsother than an alcohol suitable for use herein include tetrahydrofuran,N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

In step (a), a halogenated aromatic acid is preferably contacted with atotal of from about n+m to n+m+1 equivalents of the alcoholate RO⁻M⁺ perequivalent of halogenated aromatic acid. Between m and m+1 equivalentsis used for forming the m-basic salt and between n and n+1 equivalentsis used for the displacement reaction. It is preferred that the totalamount of alcoholate not exceed m+n+1. It is also preferred that thetotal amount of alcoholate not be less than m+n in order to avoidreduction reactions. One “equivalent” as used in this context is thenumber of moles of alcoholate RO⁻M⁺ that will react with one mole ofhydrogen ions; for an acid, one equivalent is the number of moles ofacid that will supply one mole of hydrogen ions.

As mentioned above, in step (a), the halogenated aromatic acid is alsocontacted with a copper (I) or (II) source in the presence of a diamineligand that coordinates to copper. The copper source and the ligand maybe added sequentially to the reaction mixture, or may be combinedseparately (for example, in a solution of water or acetonitrile) andadded together.

The copper source is a Cu(I) salt, a Cu(II) salt, or mixtures thereof.Examples include without limitation CuCl, CuBr, CuI, Cu₂SO₄, CuNO₃,CuCl₂, CuBr₂, CuI₂, CuSO₄, and Cu(NO₃)₂. The selection of the coppersource may be made in relation to the identity of the halogenatedaromatic acid used. For example, if the starting halogenated aromaticacid is a bromobenzoic acid, CuCl, CuBr, CuI, Cu₂SO₄, CuNO₃, CuCl₂,CuBr₂, CuI₂, CuSO₄, and Cu(NO₃)₂ will be included among the usefulchoices. If the starting halogenated aromatic acid is a chlorobenzoicacid, CuBr, CuI, CuBr₂ and CuI₂ will be included among the usefulchoices. Optionally, prior to step (a), a measured amount (˜0.25 mol ofO₂/mol of CuI) prep to dissolve CuI in the diamine/alcohol solution.CuBr and CuBr₂ are in general preferred choices for most systems. Theamount of copper used is typically about 0.1 to about 5 mol % based onmoles of halogenated aromatic acid.

The ligand may be a straight- or branched-chain or cyclic, aliphatic oraromatic, substituted or unsubstituted, diamine, or a mixture of two ofmore such ligands. In its unsubstituted form, the ligand may be adiamine that contains carbon, nitrogen and hydrogen atoms only. In itssubstituted form, the amine ligand may contain hetero atoms such asoxygen or sulfur. In various embodiments, the amine may contain at leastone primary or secondary amino group.

Primary or secondary diamines suitable for use herein as the ligandinclude those described generally by the following Formula IV

wherein each R¹ and each R² is independently

H;

a C₁˜C₁₀ straight-chain or branched, saturated or unsaturated,substituted or unsubstituted, hydrocarbyl radical;

a C₃˜C₁₂ cyclic aliphatic, saturated or unsaturated, substituted orunsubstituted, hydrocarbyl radical; or

a C₆˜C₁₂ aromatic substituted or unsubstituted hydrocarbyl radical;

wherein R³ and R⁴ are each independently

H;

a C₁˜C₁₀ straight-chain or branched, saturated or unsaturated,substituted or unsubstituted, hydrocarbyl radical;

a C₃˜C₁₂ cyclic aliphatic, saturated or unsaturated, substituted orunsubstituted, hydrocarbyl radical; or

a C₆˜C₁₂ aromatic substituted or unsubstituted hydrocarbyl radical; or

R³ and R⁴ are joined to form a ring structure that is

a C₄˜C₁₂ aliphatic, saturated or unsaturated, substituted orunsubstituted, hydrocarbyl ring structure; or

a C₆˜C₁₂ aromatic substituted or unsubstituted hydrocarbyl ringstructure; and

wherein a, b, and c are each independently 0˜4.

In certain embodiments, one or both of the R¹s is H. In otherembodiments, one or both of the R²s is also H. In other embodiments, anyone or more of R¹ to R⁴ may be a methyl, ethyl, propyl, butyl, pentyl,hexyl or phenyl radical.

In various particular embodiments, a, b and c may all equal 0, andeither R³═R⁴═H, or R³ and R⁴ are joined to form an aliphatic ringstructure. Particularly when b=0, the aliphatic ring structure may be acyclohexylene group, which is the divalent radical, —C₆H₁₀—, as shownbelow, thus providing a cyclohexyl diamine:

The formation of a cyclohexylene group from R³ and R⁴ may be illustratedgenerally by the following structure (V):

where R¹, R², a and c are as set forth above. In alternativeembodiments, however, one amino group, or the alkyl radical on which itis located, may be in the meta or para position on the cycloalkyl oraromatic ring to the other amino group.

Particularly suitable aliphatic diamines include N,N′-di-n-alkylethylenediamines and N,N′-di-n-alkylcyclohexane-1,2-diamines. Specific examplesinclude without limitation N,N′-dimethylethylene diamine,N,N′-diethylethylene diamine, N,N′-di-n-propylethylene diamine,N,N′-dibutylethylene diamine, N,N′-dimethylcyclohexane-1,2-diamine,N,N′-diethylcyclohexane-1,2-diamine,N,N′-di-n-propylcyclohexane-1,2-diamine, andN,N′-dibutylcyclohexane-1,2-diamine. Examples of suitable aromaticdiamines include without limitation 1,2-phenylenediamine andN,N′-dialkylphenylene diamines such asN,N′-dimethyl-1,2-phenylenediamine andN,N′-diethyl-1,2-phenylenediamine; and benzidine.

The “hydrocarbyl” groups referred to above in the descriptions ofligands suitable for use herein are, when unsubstituted, univalentgroups containing only carbon and hydrogen. Similarly, an unsubstitutedamine is a compound that contains in its structure nitrogen, carbon andhydrogen atoms only.

Ligands of particular versatility include secondary amines, particularlyN,N′-substituted 1,2-diamines, including those that that may bedescribed as R⁵NH—(CHR⁶CHR⁷)—NHR⁸ wherein R⁵ and R⁸ are eachindependently chosen from the group of C₁-C₄ primary alkyl radicals, andR⁶ and R⁷ are each independently chosen from the group of H and C₁-C₄alkyl radicals, and/or where R⁶ and R⁷ may be joined to form a ringstructure.

When, in Formula V, R³ and R⁴ are joined to form an aromatic ringstructure, and/or when a cyclic amine ligand contains one or morearomatic ring structures, more severe reaction conditions (e.g. highertemperature, or larger amounts of copper and/or ligand) may be needed toachieve high conversion, selectivity, yield and/or purity in thereaction.

A ligand suitable for use herein may be selected as any one or more orall of the members of the whole population of ligands described by nameor structure above.

Various copper sources and ligands suitable for use herein may be madeby processes known in the art, or are available commercially fromsuppliers such as Alfa Aesar (Ward Hill, Mass.), City Chemical (WestHaven, Conn.), Fisher Scientific (Fairlawn, N.J.), Sigma-Aldrich (St.Louis, Mo.) or Stanford Materials (Aliso Viejo, Calif.).

In various embodiments, the ligand may be provided in an amount of about1 to about 8, preferably about 1 to about 2, molar equivalents of ligandper mole of copper. In those and other embodiments, the ratio of molarequivalents of ligand to molar equivalents of halogenated aromatic acidmay be less than or equal to about 0.1. As used herein, the term “molarequivalent” indicates the number of moles of ligand that will interactwith one mole of copper.

In step (b), the reaction mixture is heated to form the m-basic saltgenerally described by Formula III:

The reaction temperature for steps (a) and (b) is preferably betweenabout 40 and about 120° C., more preferably between about 75 and about95° C. Typically, the time required for step (a) is from about 0.1 toabout 1 hour. The time required for step (b) is typically from about 0.1to about 1 hour. Optimal times and temperatures may vary depending onthe specific materials. Oxygen may be desirably excluded during thereaction. The solution is typically allowed to cool before optional step(c) and before the acidification in step (d) is carried out.

The m-basic salt of the ether of the aromatic acid is then contacted instep (d) with acid to convert it to the hydroxy aromatic acid product.Any acid of sufficient strength to protonate the m-basic salt issuitable. Examples include without limitation hydrochloric acid,sulfuric acid and phosphoric acid.

In one embodiment, the copper (I) or copper (II) source is selected fromthe group consisting of CuBr, CuBr and mixtures thereof; the ligand isselected from the group consisting of N,N′-dimethylethylene diamine,N,N′-diethylethylene diamine, N,N′-di-n-propylethylene diamine,N,N′-dibutylethylene diamine, N,N′-dimethylcyclohexane-1,2-diamine,N,N′-diethylcyclohexane-1,2-diamine,N,N′-di-n-propylcyclohexane-1,2-diamine, andN,N′-dibutylcyclohexane-1,2-diamine; and the copper (I) or copper (II)source is combined with two molar equivalents of the ligand.

The process described above also allows for effective and efficientsynthesis of products made from the resulting ethers of aromatic acidssuch as a compound, a monomer, or an oligomer or polymer thereof. Theseproduced materials may have one or more of ester functionality, etherfunctionality, amide functionality, imide functionality, imidazolefunctionality, thiazole functionality, oxazole functionality, carbonatefunctionality, acrylate functionality, epoxide functionality, urethanefunctionality, acetal functionality, and anhydride functionality.

Representative reactions involving a material made by the process ofthis invention, or a derivative of such material, include, for example,making a polyester from an ether of aromatic acid and either diethyleneglycol or triethylene glycol in the presence of 0.1% of Zn₃(BO₃)₂ in1-methylnaphthalene under nitrogen, according to the method taught inU.S. Pat. No. 3,047,536 (which is incorporated in its entirety as a parthereof for all purposes). Similarly, an ether of aromatic acid issuitable for copolymerization with a dibasic acid and a glycol toprepare a heat-stabilized polyester according to the method taught inU.S. Pat. No. 3,227,680 (which is incorporated in its entirety as a parthereof for all purposes), wherein representative conditions involveforming a prepolymer in the presence of titanium tetraisopropoxide inbutanol at 200-250° C., followed by solid-phase polymerization at 280°C. at a pressure of 0.08 mm Hg.

An ether of aromatic acid can also be polymerized with thetrihydrochloride-monohydrate of tetraminopyridine in a condensationpolymerization in strong polyphosphoric acid under slow heating above100° C. up to about 180° C. under reduced pressure, followed byprecipitation in water, as disclosed in U.S. Pat. No. 5,674,969 (whichis incorporated in its entirety as a part hereof for all purposes); orby mixing the monomers at a temperature from about 50° C. to about 110°C., and then 145° C. to form an oligomer, and then reacting the oligomerat a temperature of about 160° C. to about 250° C. as disclosed in U.S.Provisional Application. No. 60/665,737, filed Mar. 28, 2005 (which isincorporated in its entirety as a part hereof for all purposes),published as WO 2006/104974. The polymer that may be so produced may bea pyridobisimidazole-2,6-diyl(2,5-dialkoxy-p-phenylene) polymer or apyridobisimidazole-2,6-diyl(2,5-diareneoxy-p-phenylene) polymer such asa poly(1,4-(2,5-diareneoxy)phenylene-2,6-pyrido[2,3-d:5,6-d′]bisimidazole) polymer. The pyridobisimidazole portion thereofmay, however, be replaced by any one or more of a benzobisimidazole,benzobisthiazole, benzobisoxazole, pyridobisthiazole and apyridobisoxazole; and the 2,5-dialkoxy-p-phenylene portion thereof maybe replaced by an alkyl or aryl ether of one or more of isophthalicacid, terephthalic acid, 2,5-pyridine dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyl dicarboxylic acid, 2,6-quinolinedicarboxylic acid, and 2,6-bis(4-carboxyphenyl)pyridobisimidazole,wherein such an ether is produced according to the methods disclosedherein.

The polymer prepared in such manner may, for example, contain one ormore of the following units:

pyridobisimidazole-2,6-diyl(2,5-dialkoxy-p-phenylene) and/orpyridobisimidazole-2,6-diyl(2,5-diphenoxy-p-phenylene) units;

units selected from the group consisting ofpyridobisimidazole-2,6-diyl(2,5-dimethoxy-p-phenylene),pyridobisimidazole-2,6-diyl(2,5-diethoxy-p-phenylene),pyridobisimidazole-2,6-diyl(2,5-dipropoxy-p-phenylene),pyridobisimidazole-2,6-diyl(2,5-dibutoxy-p-phenylene) andpyridobisimidazole-2,6-diyl(2,5-diphenoxy-p-phenylene);

pyridobisthiazole-2,6-diyl(2,5-dialkoxy-p-phenylene) and/orpyridobisthiazole-2,6-diyl(2,5-diphenoxy-p-phenylene) units;

units selected from the group consisting ofpyridobisthiazole-2,6-diyl(2,5-dimethoxy-p-phenylene),pyridobisthiazole-2,6-diyl(2,5-diethoxy-p-phenylene),pyridobisthiazole-2,6-diyl(2,5-dipropoxy-p-phenylene),pyridobisthiazole-2,6-diyl(2,5-dibutoxy-p-phenylene) andpyridobisthiazole-2,6-diyl(2,5-diphenoxy-p-phenylene);

pyridobisoxazole-2,6-diyl(2,5-dialkoxy-p-phenylene) and/orpyridobisoxazole-2,6-diyl(2,5-diphenoxy-p-phenylene) units;

units selected from the group consisting ofpyridobisoxazole-2,6-diyl(2,5-dimethoxy-p-phenylene),pyridobisoxazole-2,6-diyl(2,5-diethoxy-p-phenylene),pyridobisoxazole-2,6-diyl(2,5-dipropoxy-p-phenylene),pyridobisoxazole-2,6-diyl(2,5-dibutoxy-p-phenylene) andpyridobisoxazole-2,6-diyl(2,5-diphenoxy-p-phenylene);

benzobisimidazole-2,6-diyl(2,5-dialkoxy-p-phenylene) and/orbenzobisimidazole-2,6-diyl(2,5-diphenoxy-p-phenylene) units;

units selected from the group consisting ofbenzobisimidazole-2,6-diyl(2,5-dimethoxy-p-phenylene),benzobisimidazole-2,6-diyl(2,5-diethoxy-p-phenylene),benzobisimidazole-2,6-diyl(2,5-dipropoxy-p-phenylene),benzobisimidazole-2,6-diyl(2,5-dibutoxy-p-phenylene) andbenzobisimidazole-2,6-diyl(2,5-diphenoxy-p-phenylene);

benzobisthiazole-2,6-diyl(2,5-dialkoxy-p-phenylene) and/orbenzobisthiazole-2,6-diyl(2,5-diphenoxy-p-phenylene) units;

units selected from the group consisting ofbenzobisthiazole-2,6-diyl(2,5-dimethoxy-p-phenylene),benzobisthiazole-2,6-diyl(2,5-diethoxy-p-phenylene),benzobisthiazole-2,6-diyl(2,5-dipropoxy-p-phenylene),benzobisthiazole-2,6-diyl(2,5-dibutoxy-p-phenylene) andbenzobisthiazole-2,6-diyl(2,5-diphenoxy-p-phenylene);

benzobisoxazole-2,6-diyl(2,5-dialkoxy-p-phenylene) and/orbenzobisoxazole-2,6-diyl(2,5-diphenoxy-p-phenylene) units; and/or

units selected from the group consisting ofbenzobisoxazole-2,6-diyl(2,5-dimethoxy-p-phenylene),benzobisoxazole-2,6-diyl(2,5-diethoxy-p-phenylene),benzobisoxazole-2,6-diyl(2,5-dipropoxy-p-phenylene),benzobisoxazole-2,6-diyl(2,5-dibutoxy-p-phenylene) andbenzobisoxazole-2,6-diyl(2,5-diphenoxy-p-phenylene).

EXAMPLES

The advantageous attributes and effects of the processes hereof may beseen in laboratory examples, as described below. The embodiments ofthese processes on which the example is based are representative only,and the selection of those embodiments to illustrate the invention doesnot indicate that conditions, arrangements, approaches, steps,techniques, configurations or reactants not described in the example arenot suitable for practicing these processes, or that subject matter notdescribed in the example is excluded from the scope of the appendedclaims and equivalents thereof.

Materials. All reagents were used as received.Rac-trans-N,N′-dimethylcyclohexane-1,2-diamine (97% purity) and sodiummethoxide (95% purity) were obtained from Aldrich Chemical Company(Milwaukee, Wis., USA). 2,5-dibromoterephthalic acid (95+% purity) wasobtained from Maybridge Chemical Company Ltd. (Cornwall, UnitedKingdom). Copper(II) bromide (“CuBr₂”) was obtained from Acros Organics(Geel, Belgium).

As used herein, the term “conversion” refers to how much reactant wasused up as a fraction or percentage of the theoretical amount. The term“selectivity” for a product P refers to the molar fraction or molarpercentage of P in the final product mix. The conversion multiplied bythe selectivity thus equals the maximum “yield” of P; the actual or“net” yield will normally be somewhat less than this because of samplelosses incurred in the course of activities such as isolating, handling,drying, and the like. The term “purity” denotes what percentage of thein-hand, isolated sample is actually the specified substance. Productpurity was determined by ¹H NMR.

The meaning of abbreviations is as follows “h” means hour(s), “mL” meansmilliliter(s), “g” means gram(s), “MeOH” means methanol, “mg” meansmilligram(s), “mmol” means millimole(s), “mol equiv” means molarequivalent, and “NMR” means nuclear magnetic resonance spectroscopy.

Example 1

In an air and moisture free environment, 4.2 g (77 mmol) of sodiummethoxide was combined with 125 g of anhydrous methanol, followed by theaddition of 5 g (15 mmol) of 2,5-dibromoterephthalic acid. Separately,103 mg (0.03 mol equiv) of CuBr₂ and 132 mg (0.06 mol equiv) ofrac-trans-N,N-dimethylcyclohexane-1,2-diamine were combined undernitrogen, followed by addition of anhydrous methanol to dissolve. Thissolution was then added to form the reaction mixture. The reactionmixture was heated to reflux with stirring for 8 h, remaining under anitrogen atmosphere. After cooling, the product was filtered, washedwith hot MeOH and dried to yield 3.5 g (14.5 mmol) of the white solid asthe bis-sodium salt. The purity was determined to be 97% by ¹H NMR. Thenet isolated yield was determined to be 95%.

Example 2

In an air and moisture free environment, 8.82 g (163 mmol) of sodiummethoxide was combined with 250 g of anhydrous methanol, followed by theaddition of 10 g (41 mmol) of 2-bromoterephthalic acid. Separately, 274mg (0.03 mol equiv) of CuBr₂ and 386 mg (0.06 mol equiv) ofrac-trans-N,N-dimethylcyclohexane-1,2-diamine were combined undernitrogen, followed by addition of anhydrous methanol to dissolve. Thissolution was then added to form the reaction mixture. The reactionmixture was heated to reflux with stirring for 8 h, remaining under anitrogen atmosphere. After cooling, the product was filtered, washedwith MeOH and dried to yield 9.80 g (40.8 mmol) of the white solid asthe bis-sodium salt. The purity was determined to be >98% by ¹H NMR. Thenet isolated yield was determined to be 99%.

Each of the formulae shown herein describes each and all of theseparate, individual compounds that can be formed in that formula by (1)selection from within the prescribed range for one of the variableradicals, substituents or numerical coefficents while all of the othervariable radicals, substituents or numerical coefficents are heldconstant, and (2) performing in turn the same selection from within theprescribed range for each of the other variable radicals, substituentsor numerical coefficents with the others being held constant. Inaddition to a selection made within the prescribed range for any of thevariable radicals, substituents or numerical coefficents of only one ofthe members of the group described by the range, a plurality ofcompounds may be described by selecting more than one but less than allof the members of the whole group of radicals, substituents or numericalcoefficents. When the selection made within the prescribed range for anyof the variable radicals, substituents or numerical coefficents is asubgroup containing (i) only one of the members of the whole groupdescribed by the range, or (ii) more than one but less than all of themembers of the whole group, the selected member(s) are selected byomitting those member(s) of the whole group that are not selected toform the subgroup. The compound, or plurality of compounds, may in suchevent be characterized by a definition of one or more of the variableradicals, substituents or numerical coefficents that refers to the wholegroup of the prescribed range for that variable but where the member(s)omitted to form the subgroup are absent from the whole group.

Where a range of numerical values is recited herein, the range includesthe endpoints thereof and all the individual integers and fractionswithin the range, and also includes each of the narrower ranges thereinformed by all the various possible combinations of those endpoints andinternal integers and fractions to form subgroups of the larger group ofvalues within the stated range to the same extent as if each of thosenarrower ranges was explicitly recited. Where a range of numericalvalues is stated herein as being greater than a stated value, the rangeis nevertheless finite and is bounded on its upper end by a value thatis operable within the context of the invention as described herein.Where a range of numerical values is stated herein as being less than astated value, the range is nevertheless bounded on its lower end by anon-zero value.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, amounts, sizes, ranges andother quantities and characteristics recited herein, particularly whenmodified by the term “about”, may but need not be exact, and may also beapproximate and/or larger or smaller (as desired) than stated,reflecting tolerances, conversion factors, rounding off, measurementerror and the like, as well as the inclusion within a stated value ofthose values outside it that have, within the context of this invention,functional and/or operable equivalence to the stated value.

Where an embodiment of this invention is stated or described ascomprising, including, containing, having, being composed of or beingconstituted by certain features, it is to be understood, unless thestatement or description explicitly provides to the contrary, that oneor more features in addition to those explicitly stated or described maybe present in the embodiment. An alternative embodiment of thisinvention, however, may be stated or described as consisting essentiallyof certain features, in which embodiment features that would materiallyalter the principle of operation or the distinguishing characteristicsof the embodiment are not present therein. A further alternativeembodiment of this invention may be stated or described as consisting ofcertain features, in which embodiment, or in insubstantial variationsthereof, only the features specifically stated or described are present.

1. A process for preparing an ether of an aromatic acid, the ether beingdescribed by the structure of Formula I

wherein Ar is a C₆˜C₂₀ monocyclic or polycyclic aromatic nucleus, R is aunivalent organic radical, n and m are each independently a nonzerovalue, and n+m is less than or equal to 8; comprising (a) contacting ahalogenated aromatic acid that is described by the structure of FormulaII

wherein each X is independently Cl, Br or I, and Ar, n and m are as setforth above, with (i) a polar protic solvent, a polar aprotic solvent oran alcoholic solvent containing the alcoholate RO⁻M⁺ (wherein M is Na orK), wherein the polar protic solvent, polar aprotic solvent or alcoholicsolvent is either ROH or is a solvent that is less acidic than ROH; (ii)a copper (I) or copper (II) source; and (iii) a diamine ligand thatcoordinates to copper, to form a reaction mixture; (b) heating thereaction mixture to form the m-basic salt of the product of step (a), asdescribed by the structure of Formula III;

(c) optionally, separating the Formula III m-basic salt from thereaction mixture in which it is formed; and (d) contacting the FormulaIII m-basic salt with acid to form therefrom an ether of an aromaticacid.
 2. A process according to claim 1 wherein the halogenated aromaticacid is selected from the group consisting of 2-bromobenzoic acid,2,5-dibromobenzoic acid, 2-bromo-5-nitrobenzoic acid,2-bromo-5-methylbenzoic acid, 2-chlorobenzoic acid, 2,5-dichlorobenzoicacid, 2-chloro-3,5-dinitrobenzoic acid, 2-chloro-5-methylbenzoic acid,2-bromo-5-methoxybenzoic acid, 5-bromo-2-chlorobenzoic acid,2,3-dichlorobenzoic acid, 2-chloro-4-nitrobenzoic acid,2,5-dichloroterephthalic acid, 2-chloro-5-nitrobenzoic acid,2,5-dibromoterephthalic acid, and 2,5-dichloroterephthalic acid.
 3. Aprocess according to claim 1 wherein, in step (a), a total of about n+mto n+m+1 normal equivalents of RO⁻M⁺ are added to the reaction mixtureper equivalent of the halogenated aromatic acid.
 4. A process accordingto claim 1 wherein the copper source comprises a Cu(I) salt, a Cu(II)salt, or a mixture thereof.
 5. A process according to claim 4 whereinthe copper source is selected from the group consisting of CuCl, CuBr,CuI, Cu₂SO₄, CuNO₃, CuCl₂, CuBr₂, CuI₂, CuSO₄, Cu(NO₃)₂, and mixturesthereof.
 6. A process according to claim 1 wherein the ligand comprisesa cyclohexyl diamine.
 7. A process according to claim 1 where the ligandcomprises an N,N′-substituted diamine.
 8. A process according to claim 7wherein the ligand comprises an N,N′-di-n-alkylethylene diamine or anN,N′-di-n-alkylcyclohexane-1,2-diamine.
 9. A process according to claim8 wherein the ligand is selected from the group consisting ofN,N′-dimethylethylene diamine, N,N′-diethylethylene diamine,N,N′-di-n-propylethylene diamine, N,N′-dibutylethylene diamine,N,N′-dimethylcyclohexane-1,2-diamine,N,N′-diethylcyclohexane-1,2-diamine,N,N′-di-n-propylcyclohexane-1,2-diamine, andN,N′-dibutylcyclohexane-1,2-diamine.
 10. A process according to claim 1further comprising a step of combining the copper source with the ligandbefore adding them to the reaction mixture.
 11. A process according toclaim 5 wherein the copper source comprises CuBr or CuBr₂.
 12. A processaccording to claim 1 wherein copper is provided in an amount of betweenabout 0.1 and about 5 mol % based on moles of halogenated aromatic acid.13. A process according to claim 1 wherein the ligand is provided in anamount of between about one and about two molar equivalents per mole ofcopper.
 14. A process according to claim 1 wherein R is selected fromthe group consisting of C₁˜C₁₂ alkyl groups, aryl groups and the groupsgenerally described by the following formulae:


15. A process according to claim 14 wherein R comprises a C₁˜C₄ alkylgroup or phenyl group.
 16. A process according to claim 1 wherein thealcoholic solvent comprises ROH.
 17. A process according to claim 1wherein the halogenated aromatic hydroxy acid comprises2,5-dibromoterephthalic acid or 2,5-dichloroterephthalic acid; Rcomprises methyl, ethyl, i-propyl, i-butyl or phenyl; the alcoholicsolvent comprises ROH; the copper source comprises CuBr, CuBr₂ or amixture of CuBr and CuBr₂; the copper source is provided in an amount ofbetween about 0.1 and about 5 mol % based on moles of halogenatedaromatic acid; the ligand is selected from the group consisting ofN,N′-dimethylethylene diamine, N,N′-diethylethylene diamine,N,N′-di-n-propylethylene diamine, N,N′-dibutylethylene diamine,N,N′-dimethylcyclohexane-1,2-diamine,N,N′-diethylcyclohexane-1,2-diamine,N,N′-di-n-propylcyclohexane-1,2-diamine,N,N′-dibutylcyclohexane-1,2-diamine; and the ligand is provided in anamount of between about one and about two molar equivalents per mole ofcopper.
 18. A process according to claim 1 further comprising a step ofsubjecting the ether of the aromatic acid to a reaction to preparetherefrom a compound, monomer, oligomer or polymer.
 19. A processaccording to claim 18 wherein a polymer prepared comprises at least onemember of the group consisting of pyridobisimidazole, pyridobisthiazole,pyridobisoxazole, benzobisimidazole, benzobisthiazole, andbenzobisoxazole moieties.
 20. A process according to claim 19 wherein apolymer prepared comprises apyridobisimidazole-2,6-diyl(2,5-dialkoxy-p-phenylene) polymer or apyridobisimidazole-2,6-diyl(2,5-diareneoxy-p-phenylene) polymer.